This application claims the priority of German patent document 100 15 654.1, filed Mar. 29, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a fuel cell system having a gas generation system for providing hydrogen from a carbon and hydrogen containing medium, and to a method for operating such a fuel cell system.
In fuel cell powered vehicles, which are operated by hydrogen-containing fluids, such as for example methanol, the response time of the gas generation system is essential to the dynamics of the vehicle. In response to a changed power demand from the driver, for example, more or less hydrogen is generated from methanol in the gas generation system and is provided to the fuel cell. To provide a sufficiently short reaction time of the system, it has been proposed, for example, to use reactors which are as compact as possible and have short gas flow paths in the gas generation system. Such a gas generation system is disclosed, for example, in German patent document DE 197 46 251 C2.
One object of the present invention therefore is to provide a fuel cell system and a method of operating a fuel cell system, which achieve improved dynamic response to changing power demands.
This and other objects and advantages are achieved by the gas generation system and method according to the invention, which includes provision for adjusting pressure in the gas generation system and/or a mass flow through the fuel cell unit, as a function of a load on the fuel cell unit, upstream of a fuel cell unit. In the event of a transition from a part-load range to a full-load range, the pressure can be at least briefly reduced and in the event of a transition from a full-load range to a part-load range, the pressure can be at least briefly increased.
It is beneficial to provide means for pressure regulation, in order to adjust the pressure in the part-load range and/or full-load range.
It is particularly beneficial to provide means for mass-flow regulation, in order to regulate a mass or volumetric flow of a medium supplied to the fuel cell unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.